The Kurdish-led Syrian Democratic Forces (SDF) said Turkey and its Syrian rebel allies had launched a large land offensive targeting three villages on Thursday despite a truce and urged the United States to intervene immediately to stop the attack.
In a statement, the SDF said the attack by Turkish forces on the villages "outside the area of the ceasefire" had forced thousands of civilians to flee. "Our forces are still clashing," it said.
The SDF held Turkey responsible for "deterioration of the ceasefire process", it added.
"Despite our forces' commitment to the ceasefire decision and the withdrawal of our forces from the entire ceasefire area, the Turkish state and the terrorist factions allied to it are still violating the ceasefire process," it said.
Separately, SDF official Mustafa Bali said in a Tweet that the SDF would exercise its legitimate right to self defence.